Headrests are components which are attached to seats, such as a driver's seat of a vehicle and a passenger's seat thereof, and which support the head of a sitting person. Some headrests include a framework to which a cushioning member is attached, and a stay that supports the framework, and allows the position adjustment of the framework in the back-and-forth direction in accordance with the posture of the sitting person and the body type thereof. Such headrests are provided with a mechanism that prevents the framework from moving backwardly so as not to allow the head to move backwardly due to shock from a collision.
For example, Patent Literatures 1-4 disclose headrests that include a stay, a link member coupled to the stay in a turnable manner, a framework coupled to the link member in a turnable manner, and a ratchet member that is capable of restricting the turning of the link member. Those headrests allow the position adjustment of the framework in the back-and-forth direction by the turning link member. In addition, the ratchet member prevents the framework from moving backwardly.
Patent Literature 5 discloses a headrest that includes a framework turnable in the back-and-forth direction, a stay that turns relative to the framework, and a coil spring attached so as to tighten the stay. The coil spring is wound in such a way that the direction in which the stay relatively turns when the framework turns backwardly is the direction in which the number of windings of the coil spring increases, and has one end stationary fixed to the framework. According to this headrest, when the framework is pushed forwardly, the framework turns together with the end of the coil spring, the winding of the coil is loosened, and thus the tightening force for the stay by the coil spring decreases. Hence, the framework can be pushed forwardly, and the position thereof can be adjusted in a stepless manner. Conversely, when the framework is pushed backwardly, the end of the coil spring turns in a direction in which the windings of the coil increases, the coil spring tightens the turning stay relative to the framework, and thus the backward movement of the framework is restricted.